Subsection M261Ea
Diamond Mountain - Crystal Peak

Lithology and Stratigraphy.  Mesozoic granitic rocks, mostly hornblende - biotite granodiorite, predominate in this subsection.  There are lesser amounts of Eocene nonmarine sedimentary rocks and post-Eocene andesite, basalt, rhyolite, and pyroclastic rocks.  Some sedimentary deposits are intercalated with the late Tertiary volcanic rocks.

Geomorphology.   This section includes a steep fault-line scarp, or Honey Lake fault escarpment, and a rolling plateau.  The escarpment is the northeast margin of the Sierra Nevada.  It is aligned toward the northwest, curving around toward the west-northwest at the northern end.  The high plateau is a gently sloping to moderately steep fluvial erosion surface, some of which has been modified slightly by glaciation.  It is capped by remnants of volcanic rock along the ridge above the Honey Lake fault escarpment, on Red Rock, Wildcat Ridge, and a few other high ridges.  Indian Creek has cut a deep canyon across the plateau. The elevation ranges from about 4000 feet along Indian Creek and 4200 at the bottom of the Honey Lake fault escarpment, to 7738 feet on Diamond Mountain, 7795 feet on Thompson Peak, and 8197 feet on Adams Peak.  Faulting,  mass wasting, and fluvial erosion are the main geomorphic processes.

Soils.  The soils are mostly shallow Typic and Dystric Xeropsamments; Typic and Entic Xerumbrepts; and, at lower elevations, Ultic Haploxeralfs.  Those on volcanic rocks are mostly Lithic and Andic Xerumbrepts; Typic Argixerolls; and Andic Haploxeralfs.  The soils are mostly well drained.  Soil temperature regimes are mostly frigid, with some mesic.  Soil moisture regimes are xeric.

Vegetation.   The predominant natural plant communities are Jeffrey pine series and White fir series, and at lower elevations Mixed conifer series.  Small areas of Red fir series are present higher elevations.  Big sagebrush series and Low sagebrush series are common on very stony and shallow soils in volcanic terrain.  The most common streamside riparian communities are Black cottonwood series at lower elevations and Mountain alder series at higher elevations.  Lodgepole pine series and Aspen series are common, but not extensive.  Sedge meadow communities occur in wet areas.

Characteristic series by lifeform include:
Grasslands: Ashy ryegrass series, Green fescue series, Idaho fescue series, Montane meadow habitat, Nebraska sedge series, Needle-and-thread series, Rocky Mountain sedge series.
Shrublands: Big sagebrush series, Bitterbush series, Greenleaf manzanita series, Low sagebrush series, Parry rabbitbrush series, Rubber rabbitbrush series, Tobacco brush series.
Forests and woodlands: Aspen series, Baker cypress stands, Jeffrey pine series, Jeffrey pine - ponderosa pine series, Lodgepole pine series, Ponderosa pine series, Red fir series, Western white pine series, White fir series.

Surface Water.  Runoff is rapid from most of the area.  There are a few small lakes, or ponds, in glaciated terrain.  Streams on the Honey Lake escarpment drain to Honey Lake.  Those on the plateau west of the escarpment drain through Indian Creek to the Feather River.